A nonaqueous electrolyte battery using titanium oxide as the negative electrode has less possibility of the generation of lithium dendrite than a battery using a carbonaceous material because titanium oxide has a higher Li-absorbing and releasing potential than that of the carbonaceous material. Also, titanium oxide is resistant to thermorunaway because titanium oxide is ceramics. This is the reason why a nonaqueous electrolyte battery using titanium oxide as the negative electrode is highly safe. Especially, a spinel type lithium titanate having spinel structure is not varied in volume by a charge-discharge reaction and is therefore a promising material as a negative electrode active material having excellent cycle performance and high safety. However, a nonaqueous electrolyte battery using titanium oxide has the problem that it has a low energy density. For example, the theoretical capacity of titanium dioxide having an anatase structure is about 160 mAh/g and the theoretical capacity of lithium-titanium complex oxide having a spinel structure such as Li4Ti5O12 is about 170 mAh/g.
In light of this situation, much attention is now focused on a titanium oxide compound having a monoclinic titanium dioxide crystal structure. The reversible capacity of the titanium oxide compound having a monoclinic titanium dioxide crystal structure is about 240 mAh/g which is a significantly higher than those of other titanium oxide compounds.
However, when the titanium oxide compound having a monoclinic titanium dioxide crystal structure is used as the negative electrode, this poses a problem concerning a reduced cycle life.